Comparative 48-Week Viral Load Suppression across Antiretroviral Initiation Regimens: Dolutegravir versus Non-Dolutegravir among People Living with HIV in Tanzania

A retrospective analysis of routine HIV programme data in Tanzania involving nearly 7,000 patients demonstrates that antiretroviral therapy initiation with dolutegravir-based regimens results in significantly higher 48-week viral load suppression rates (91.7%) compared to non-dolutegravir regimens (86.7%).

The Gist

Imagine the fight against HIV as a long-distance marathon. The goal isn't just to start running; it's to keep running steadily so that the "virus" (the opponent) doesn't catch up. In this race, the runners are people living with HIV, and the "shoes" they wear are their daily medications, known as antiretroviral therapy (ART).

For a long time, the standard shoes were made of one material (older drugs). Recently, a new, high-tech material called Dolutegravir (DTG) was introduced, promising to be faster, more durable, and harder for the opponent to break through.

This study is like a massive race report from Tanzania, looking at thousands of runners to see: Did the new shoes help people stay ahead of the virus better than the old shoes?

Here is the breakdown of what the researchers found, using simple analogies:

1. The Setup: A Giant Race Database

The researchers didn't just ask a few people how they felt. They dug into the national "scoreboard" (a massive database) containing records of nearly 50,000 runners. They zoomed in on 6,991 runners who had a specific check-up exactly 48 weeks (about a year) after they started their race.

• The Goal: To see if their "virus count" (the opponent's score) was low enough to be considered "suppressed" (safe).
• The Groups: They split the runners into two teams:
  • Team Old Shoes: Started on older, non-DTG medications.
  • Team New Shoes: Started on the newer DTG-based medications.

2. The Raw Results: Who Won the First Lap?

When they looked at the raw numbers without adjusting for anything else, Team New Shoes looked like the clear winners.

• 91.7% of the New Shoes team had successfully suppressed the virus.
• 86.7% of the Old Shoes team did the same.

It looked like the new shoes were simply superior. But in a marathon, you have to look closer. Did the New Shoes team start the race later? Did they have better coaches? Did they run in better weather?

3. The Twist: The "Time Travel" Effect

When the researchers adjusted the data to account for when the runners started, the story changed.

• The Old Shoes team mostly started their race back in 2017–2018.
• The New Shoes team mostly started later, in 2020–2021.

Think of it like this: The New Shoes team didn't just get better shoes; they also got better weather (improved healthcare systems, better training programs, and more experience from the country over time).

When the researchers compared the two teams fairly (accounting for the year they started and how well they stuck to their training), the difference disappeared.

• The "New Shoes" didn't statistically beat the "Old Shoes" once you realized the New Shoes team had a head start in time and support.
• The real winners were the runners who stuck to their training (adherence) and the runners who started later when the whole country's support system was stronger.

4. The "Rescue" Story: When Runners Stumble

The study also looked at runners who stumbled (their virus count went up) while wearing the Old Shoes.

• Many of these runners were told to switch to the New Shoes (DTG).
• The Result: It was like giving a runner a turbo-boost. Even if they had been struggling with their training (adherence) before, switching to the New Shoes helped them get back on track very quickly. The New Shoes are "forgiving"—they are harder for the virus to outsmart, even if the runner misses a few steps.

5. The Big Takeaway

So, what does this mean for the general public?

• Both shoes work: The older medications (like TDF+3TC+EFV) are still very strong. If you are already running well with them, you don't need to panic.
• The new shoes are great: The newer DTG medications are excellent, especially for people who have struggled with the older ones or need a "safety net" because they sometimes forget to take their meds.
• The most important factor is YOU: The study found that the single biggest predictor of winning the race wasn't the brand of shoe, but how consistently you wore them. If you take your meds every day, you win, regardless of whether you are on the old or new regimen.
• Timing matters: The country got better at managing the race over time. Starting treatment in 2020 was easier and more successful than starting in 2017, simply because the support system improved.

In a nutshell: Tanzania's HIV program is doing a fantastic job. Whether you are on the "classic" regimen or the "new and improved" one, the goal is the same: keep taking your meds, and the virus will stay suppressed. The new drugs offer a powerful safety net, but the old ones are still champions in their own right.

Technical Summary

1. Problem Statement

Despite the global shift toward Dolutegravir (DTG)-based antiretroviral therapy (ART) as the preferred first-line regimen due to its high genetic barrier to resistance and tolerability, there is a lack of national-level evidence in Tanzania comparing virologic outcomes between DTG and non-DTG initiation regimens.

• Gap in Literature: Existing Tanzanian analyses are largely cross-sectional or focus on viral load testing uptake rather than longitudinal outcomes at a fixed clinical milestone.
• Need: There is a need to anchor virologic outcomes to a specific post-initiation time point (48 weeks) to reduce temporal variability caused by programmatic scale-up and evolving treatment policies, allowing for a direct comparison of early treatment effectiveness across different regimens.

2. Methodology

Study Design & Data Source:

• Type: Retrospective cohort analysis.
• Data Source: Routinely collected data from the Tanzania National AIDS, STIs, and Hepatitis Control Programme (NASHCoP) Care and Treatment Clinic (CTC) database.
• Sample Construction:
  • Initial dataset: 49,547 unique patients (derived from a random sample of 50,000 IDs) with over 1 million clinical visits.
  • Inclusion Criteria: Patients with a documented viral load measurement approximately 48 weeks (± programmatic window) after ART initiation.
  • Final Analytic Cohort: 6,991 patients.

Exposure & Outcome Definitions:

• Primary Exposure: ART regimen at initiation, categorized as DTG-based (containing Dolutegravir) vs. Non-DTG (NNRTI-based or other non-DTG regimens).
• Primary Outcome: Viral load suppression at 48 weeks, defined as <1,000 copies/mL.
• Covariates: Age, gender, average adherence (pharmacy refill-based), and calendar year of ART initiation (2017–2021).

Statistical Analysis:

• Descriptive: Summarized baseline characteristics and temporal trends.
• Crude Comparison: Compared suppression rates between DTG and non-DTG groups.
• Multivariate Logistic Regression: Assessed the association between regimen type and suppression, adjusting for age, gender, adherence, and calendar year.
• Secondary Analyses: Examined Treatment Change Episodes (TCE), early switching patterns, and longitudinal clinical trajectories (Swimmer plots and 4-panel integrated trajectories).

3. Key Results

Demographics & Baseline Characteristics:

• Cohort: Mean age 37.6 years; 64.5% female; mean adherence 86.9%.
• Group Differences: DTG initiators were slightly younger, had lower adherence, fewer clinic visits, and shorter follow-up durations compared to non-DTG initiators.
• Temporal Shift: Non-DTG initiators were concentrated in 2017–2018, while DTG initiators were concentrated in 2020–2021, reflecting the national policy transition.

Viral Load Suppression (Crude Analysis):

• Overall Suppression: 87.4% (6,113/6,991) achieved suppression at 48 weeks.
• By Regimen:
  • DTG-based: 91.7% (917/1,000).
  • Non-DTG: 86.7% (5,196/5,991).
• Specific Regimens: The most common non-DTG regimen (TDF+3TC+EFV) showed 89.7% suppression; the most common DTG regimen (TDF+3TC+DTG) showed 91.8% suppression.

Multivariate Analysis (Adjusted):

• Regimen Effect: After adjusting for adherence and calendar year, DTG initiation was NOT significantly associated with higher odds of suppression compared to non-DTG (Adjusted OR: 0.98; 95% CI: 0.71–1.37; p=0.924).
• Significant Predictors:
  • Calendar Year: Later years (2019, 2020) were strongly associated with higher suppression odds compared to 2017.
  • Adherence: Higher adherence significantly increased odds of suppression (aOR 1.02 per % increase).
  • Age: Older age at initiation was associated with higher suppression.
  • Gender: Males had lower odds of suppression compared to females.

Treatment Dynamics:

• Switching: The predominant optimization pathway was transitioning from TDF+3TC+EFV to TDF+3TC+DTG (69.4%).
• Virologic Rescue: Longitudinal case studies indicated that patients with prior adherence dips and virologic failure on NNRTI regimens achieved rapid and sustained suppression after switching to DTG.

4. Key Contributions

1. Fixed-Time Point Analysis: Unlike previous cross-sectional studies in Tanzania, this study anchors outcomes to a strict 48-week post-initiation milestone, providing a more controlled comparison of regimen effectiveness.
2. Disentangling Confounders: The study demonstrates that the apparent superiority of DTG in crude analysis is largely driven by temporal programmatic improvements (scale-up, better testing access) and adherence patterns rather than the regimen itself in this specific dataset.
3. Real-World Evidence of Transition: It documents the rapid scalability of the national DTG transition, showing that programmatic optimization (switching from NNRTI to DTG) effectively rescues patients with prior virologic failure.
4. Validation of Non-DTG Regimens: The study confirms that non-DTG regimens (specifically TDF+3TC+EFV) achieved high suppression rates (89.7%) during the transition period, validating the effectiveness of the previous standard of care in routine settings.

5. Significance

• Policy Implications: The findings support the continued national rollout of DTG-based regimens, not only for their biological advantages (high barrier to resistance) but also as a critical tool for "virologic rescue" in patients failing older regimens.
• Programmatic Insight: The lack of statistical significance after adjustment highlights that programmatic maturity (improvements in testing, retention, and care delivery over time) is a major driver of improved viral suppression, sometimes overshadowing regimen-specific effects in observational data.
• Clinical Context: The study reinforces that adherence remains the most critical modifiable factor for treatment success, regardless of the regimen chosen.
• Limitations: The authors acknowledge potential selection bias (only 14% of the initial warehouse had 48-week viral loads) and residual confounding, noting that the observational nature limits causal inference.

Conclusion:
While DTG-based regimens showed higher crude viral suppression rates at 48 weeks in Tanzania, this advantage was not independent of calendar time and adherence. The study confirms that both DTG and non-DTG regimens can achieve high suppression rates in routine care, with the transition to DTG serving as a highly effective strategy for optimizing treatment outcomes and managing virologic failure.